Spain's Joaquim Rodriguez took the race leader's red jersey after the 16th stage of the Vuelta a Espana.
The 185km stage was won by Trek's Frank Schleck of Luxembourg.
Rodriguez's late acceleration on a punishing 7km climb to a summit finish at Ermita de Alba Quiros allowed him to take a one-second lead over Fabio Aru.
Katusha's Rodriguez finished ninth, almost nine minutes behind Schleck. Aru, who led by one second overnight, was two seconds further back.
Schleck dropped Rodolfo Torres 3km from the summit of the final climb, eventually finishing 1min 10secs ahead of the Colombian.
It was Schleck's first win since he served a one-year doping ban after testing positive for Xipamide, a diuretic, during the 2012 Tour de France.
Giant-Alpecin's Tom Dumoulin, is 1min 51secs behind Rodriguez in fourth heading into Tuesday's rest day and the Dutchman is expected to take the lead after Wednesday's individual time trial in Burgos.
Rodriguez, who is not renowned as a time trial specialist, expects Dumoulin, who has surprised many by keeping in touch with the climbers, to take the red jersey on Wednesday.
"After the rest day he will be concentrated on having a great time trial," said Rodriguez. "For me to win the Vuelta, he would have to slip up and I would have to have a perfect day.''
However, on his chances of winning the race, Dumoulin said: "After Wednesday we will know a bit more. Even if my time trial is really good, there will be three hard days to go."
The penultimate stage of the race, on Saturday, features four category one mountain climbs which will have a say in determining who wins the overall title.
The 21-stage Grand Tour finishes in Madrid on Sunday, 13 September.
Stage 16 result:
1. Frank Schleck (Lux/Trek) 5hrs 49mins 56secs
2. Rodolfo Torres (Col/Colombia) +1min 10secs
3. Moreno Moser (Ita/Cannondale) +1min 48secs
4. George Bennett (NZ/LottoNL) +2mins 42secs
5. Pierre Rolland (Fra/Europcar) +2mins 49secs
6. Omar Fraile (Spa/Caja Rural) +3mins 5secs
7. Carlos Verona (Spa/Etixx - Quick-Step) +4mins 26secs
8. Larry Warbasse (USA/IAM Cycling) +6mins 2secs
9. Joaquim Rodriguez (Spa/Katusha) +8mins 51secs
10. Fabio Aru (Ita/Astana) +8mins 53secs
General classification after stage 16:
1. Joaquim Rodriguez (Spa/Katusha) 67hrs 52 mins 44secs
2. Fabio Aru (Ita/Astana) +1sec
3. Rafal Majka (Pol/Tinkoff - Saxo) +1min 35secs
4. Tom Dumoulin (Ned/Giant) +1min 51secs
5. Mikel Nieve (Spa/Team Sky) +2mins 32secs
6. Esteban Chaves (Col/Orica) +2min 38secs
7. Daniel Moreno (Spa/Katusha) +2mins 49secs
8. Nairo Quintana (Col/Movistar) +3mins 11 secs
9. Alejandro Valverde (Spa/Movistar) +3mins 58secs
10. Louis Meintjes (SA/ Team MTN) +5mins 22secs